Nephrotic syndrome and renal failure after allogeneic stem cell transplantation: Novel molecular diagnostic tools for a challenging differential diagnosis

Background: Sudden onset of nephrotic syndrome after allogeneic stem cell transplantation is rare and has been associated mostly with membranous glomerulonephritis related to chronic graft-versus-host disease (cGVHD). We report a case of nephrotic syndrome and rapidly progressive renal failure occurring in a young woman 3 years after allogeneic stem cell transplantation from her HLA-identical brother. In the renal biopsy, a diffuse mononuclear cell infiltrate was observed. Furthermore, histological analysis, immunofluorescence, and electron microscopy of the kidney specimen defined the diagnosis as minimal change disease, a T-cell-mediated glomerulopathy associated with lymphoproliferative disorders, but that has never been described as an isolated manifestation of cGVHD. Methods: The differential diagnosis was performed by using immunohistochemistry and laser capture microdissection combined with Taq-Man quantitative polymerase chain reaction. Results: Infiltrating mononuclear cells in renal tissue consisted of T cells expressing DNA levels of a Y chromosome-specific gene quantitatively similar to those observed in a male subject, showing that these cells derived from the transplant donor and definitely excluding leukemia relapse. However, the large number of infiltrating T cells allowed the possibility that in this patient, minimal change disease could be related to an atypical form of GVHD. Conclusion: This is the first study to use molecular techniques to show the differential diagnosis of nephrotic syndrome after allogeneic stem cell transplantation. This novel method approach might represent a key tool to characterize kidney infiltrate after allogeneic stem cell transplantation.